Process for washing solvent laden filaments

ABSTRACT

A method and apparatus for improving the extraction of solvent from a textile rope. Solvent-laden filaments emanating from a plurality of spinning cells are combined into a rope then while being piddled into a container through an oscillating spout, the rope is sprayed with cooled extraction liquor that has been obtained from the tank of a washdraw machine. Spray heads are attached to the oscillating piddler spout to provide uniform distribution of the liquor on the rope and a foraminous false bottom in the container with a means to drain the container of liquid increases the extraction efficiency of the system.

United States Patent 1191 Singh Oct. 23, 1973 [5 PROCESS FOR WASHING SOLVENT 3,124,631 3/1964 Davis et al. 264/290 LADEN FILAMENTS [75] Inventor; prem prakash Singh, Primary Examiner-Mayer Weinblatt Charlottesville Att0rneyHoward P. West, Jr.

[73] Assignee: E. l. du Pont de Nemours and Company, Wilmington, Del. [57] ABSTRACT [22] Filed; Nov. 17, 1971 A method and apparatus for improving the extraction Appl. No.: 199,595

References Cited UNITED STATES PATENTS 10/1952 Flannagan 264/290 X of solvent from a textile rope. Solvent-laden filaments emanating from a plurality of spinning cells are'combined into a rope then while being piddled into a container through an oscillating spout, the rope is sprayed with cooled extraction liquor that has been obtained from the tank of a washdraw machine. Spray heads are attached to the oscillating piddler spout to provide uniform distribution of the liquor on the rope and a foraminous false bottom in the container with a means to drain the container of liquid increases the extraction efficiency of the system.

4 Claims, 2 Drawing Figures COO LE R PAIENIEnn'c 23 um sum 10F 2 INVENTOR PREM PRAKASH SINGH BY M19417 mmJOOQ ATTORNEY v PATENTEI] 081 2 3 I975 SHEET 2 BF 2 FIG.

ATTORNEY PROCESS FOR WASHING SOLVENT LADEN FILAMENTS BACKGROUND OF THE INVENTION Referring to FIG. 1, a plurality of spinning cells 10,

Thi inv ti i concerned i h h production f 5 similar to those described in U. S. Pat. No. 2,615,198,

synthetic filaments or yarns and specifically with improved extraction of solvent from dry spun acrylonitrile polymer fibers. Dry spun acrylonitrile polymer filaments as disclosed by Flannagan in U. S. Pat. No. 2,615,198 generally issue from a spinning cell in a so]- vent-laden condition and in the production of suitable textile yarns it is necessary to reduce the solvent content. One method of solvent extraction involves concurrently washing and drawing the filaments in a cascading water bath as disclosed by Davis and Palmer in U. S. Pat. No. 3,124,631. Prior to such wash-draw processes, it has been customary to combine a large number of yarns coming from individual spinning cells into a composite grouping of yarns usually referred to as a rope and sometimes as a tow. This rope was then deposited in a large storage container called a spinning can. When a large number of full cans'had been accumulated, they were placed in a creel arrangement so that the individual ropes were combined into a large row for solvent extraction, drawing and crimping. lt has been found on occasion that this technique of combining warm yarns into a rope, placing the rope in a can with little cooling lead to variations between yarns in their tensile history, variations in temperature history along the rope throughout the can and variations in the amount of solvent eventually extracted. These variations sometimes result in unacceptable final product dyeability and structure variability.

SUMMARY OF THE INVENTION In theproduction of rope from dry spun solventladen polyacrylonitrile filaments including the steps of combining filaments from a plurality of spinning cells into a composite rope, piddling therope into a container, forwarding the rope from said container to a liquid bath for washing to extract solvent, and withdrawingwash liquor from the bath, the improved method for extracting solvent from the rope comprising: cooling the withdrawn wash liquor and applying the cooled wash liquor to the rope prior to the washing step. Yarns emanating from th'enumerous spinning cells of a spinningmachine are combined into a rope which is then BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is apartial schematic flow diagram of the processinto which the improved extraction method is incorporated.

FIG. 2 is a perspective elevation of the oscillating piddler spout with attached sprays in association with the false bottom rope container.

produce a number of solvent-laden yarns 12, which are passed around roller guides 14 and gathered into a composite rope 16 being forwarded by pull rolls 18. The rope is then piddled'by means of piddler 20 and associated spout 22 into an open top container 24 where it is held for future processing in combination with similarly prepared ropes. This further processing is carried out in a wash-draw machine part of which is indicated at 30 in the drawing. The operation is similar to that disclosed by Davis and Palmer in U. S. Pat. No. 3,124,631. More particularly, ropes 16are combined over creel forming rollers 15 into tow 17 which is passed via rolls l9 alternately over and under rolls 31, 32, 33 and 34 in wash-draw machine 30.

An outlet valve 35 is placed in the bottom of the first tank at the tow inlet end of wash-draw machine 30 in order to withdraw wash liquor. This liquor is forced by means of a pump 36rthrough pipe 38 to a cooler or 'heat exchanger 40. From cooler 40, the liquor is transmitted through pipe 42 and flexible connector 44 to the spray nozzles 46 attached above container 24 on the lower end of spout 22. An additional valve 43 and flowmeter 45 are provided to control flow through spray nozzles 46.

An outlet pipe 25 is connected from the true bottom 28 of container 24 through valve 23 to pump 27 which exhausts liquor from the bottom of the container out through pipe 29 to a solvent recovery apparatus not shown. Container 24 is provided with a foraminous false bottom 26 located a short distance above the-true bottom 28 of the container. Alternatively, the liquor may be withdrawn from the bottom of container 24 through a vertical pipe 25 'extending down in one corner of container 24 through false bottom 26 with its open end nearly to true bottom 28 and connected at its other end to pump 27.

Referring now to FIG. 2, rope 16 is passed through a pair of rolls 18 into a piddler 20 which may be either a gear piddler or a belt piddler depending on the moisture content of rope l6, e.g., high moisture content would dictate the use of a gear piddler. From piddler 20, rope l6 falls to piddler laydown spout 22 which is supported in a gimmal arrangement as described, for example by Mendes in U. S. Pat. No. 3,378,898. More particularly, a pair of brackets 50 are attached to spout 22 adjacent its upper end and carry opposed stub shafts 52, 54. A mounting fork 56 is pivotally attached to-stubshafts 52. A second fork 58 is pivotally attached to stub shafts 54 on brackets 50. The forks. 56 and 58 are mounted for reciprocal rotational and reciprocal linear movement, respectively, as indicated by the direction arrows. The spout is thus pivotally mounted to swing simultaneously about intersecting axes to lay the rope 16' in a uniform layered manner in container 24. The container has a foraminous false bottom 26 spaced a distance d above the true or closed bottom 28. The distance d is generally selected to provide sufficient volume between the false bottom 26 and true bottom 28 to contain the liquid which percolates through the rope after the can has been removed from the filling station, pumped out, and held for further processing steps. During the step, while rope 16 is being laid in can 24 and liquid sprayed thereon by nozzles 46, the distance d between true and false bottoms provides a reservoir for convenient operation of the liquid withdrawal system. Preferably, four nozzles 46 are mounted to the lower end of spout 22 in such a manner as to uniformly distribute the liquor on rope l6.

Comparisons were made of a conventional extraction method an apparatus as taught by U. S. Pat. No. 3,124,631 and the extraction method and apparatus of this invention as used in the product of acrylonitrile fiber tow dry spun from a solvent such as dimethyl formamide (DMF) as taught in U. S. Pat. No. 2,615,198. The former extraction method is called control and the latter the test. It was found that the test process required on the average 47.5 percent less wash water per unit weight of tow produced. In addition, it was found that the test tow contained 28.2 percent less residual DMF than the control tow. Finally, the extraction liquor (DMF in water) obtained from the test process contained an average of 80 percent and up to 160 percent more DMF than for the case of the control process.

From this, it is readily apparent that the decreased water consumption, decreased residual solvent content in the end product tow and the increased concentration of extracted solvent in liquor sent to recovery provide not only monetary savings but also significant improvement in the final product.

What is claimed is:

1. In a process for providing rope from dry spun solvent-laden polyacrylonitrile filaments including the steps of combining filaments from a plurality of spinning cells into a composite rope, piddling the rope into a container, forwarding the rope from said container to a wash-draw machine, washing the rope in a bath of wash liquor in the wash-draw machine, and withdrawing wash liquor from the bath, the improvement comprising: cooling the withdrawn wash liqor in a cooler; applying the cooled wash liquor to the rope while the rope is being piddled into the container; and withdrawing surplus wash liquor from the container.

2. The process as defined in claim 1, said cooled wash liquor being sprayed on the tow as it is being piddled into the container, and then drained from said container.

3. The process as defined in claim 1, wherein ropes from a plurality of containers are combined and forwarded as a composite tow to said wash-draw machine.

4. The process as defined in claim 1, said wash liquor being water and solvent, said solvent being dimethyl formamide. 

2. The process as defined in claim 1, said cooled wash liquor being sprayed on the tow as it is being piddled into the container, and then drained from said container.
 3. The process as defined in claim 1, wherein ropes from a plurality of containers are combined and forwarded as a composite tow to said wash-draw machine.
 4. The process as defined in claim 1, said wash liquor being water and solvent, said solvent being dimethyl formamide. 